Many biological techniques, such as immunoassays, affinity purification etc., require the separation of bound from free fractions. Magnetic particles have been used to facilitate the desired separation.
Magnetic particles have been formed from a variety of particulate and magnetic matter, using a variety of processes, having different characteristics. For example, Ikeda et. al. U.S. Pat. No. 4,582,622, discloses a magnetic particle comprised of gelatin, water-soluble polysaccharide, sodium phosphate and ferromagnetic substances; U.S. Pat. Nos. 4,628,037 and 4,554,088 disclose magnetic particles comprised of a magnetic metal oxide core surrounded by a coat of polymeric silane; U.S. Pat. No. 4,452,773 discloses discrete colloidal sized particles having a core of ferromagnetic iron oxide (Fe.sub.3 O.sub.4) which is coated with a water-soluble polysaccharide or a derivative thereof having functional groups; and Mansfield U.S. Pat. No. 4,297,337 discloses magnetic glass- or crystal-containing material as a particulate carrier.